I've had a handful of chemicals in storage which have degraded their polycone caps over the course of about 1 year. One was trimethylchlorosilane and
another was cyclopentanone. The failure mode seems to be diffusing through or around the PE cone and then rapidly attacking the phenolic plastic. In
the case of the TMCS, some of the degraded phenolic actually made its way around the cone somehow and fell into the liquid, reacting with it and
turning it a light brown.
These two were purchased on eBay from Consolidated Chemical Supply and were in their original glass containers/original caps.
I've looked around for a chemical compatibility chart for the polycone caps but surprisingly I can't find one. I guess I can just look for HDPE and
phenolic charts? One problem there is that I also need to know whether the said chemical will permeate HDPE significantly, not just whether it will
attack it.
Any ideas or suggestions? So far, I replaced the TMCS cap with one of those PTFE lined melamine caps.
As an aside/warning to newbies, do not assume that eBay sellers know what appropriate packaging is. I bought chlorobenzene from one fairly big eBay
chemical supplier and when it arrived it had dissolved a good bit of its cap, which was just a foam-lined child safety cap.
Sean Dr.Bob - 9-12-2018 at 20:08
Plastic like HDPE is not ideal for harsh organics. And cheap plastic caps and liners are a pain, Aldrich used to use some of those (cone type
liner), but has mostly moved away from them. I would suggest just transferring the materials in poor containers to a glass bottle with a PTFE lined
cap, like the Qorpak ones. I have to do that sometimes with commercial chemicals from some vendors, or in things shipping in glass ampules.
I still have a few smaller Qorpak bottles for sale, and I am willing to sell small numbers of them for that purpose. I have a fair number of new 60
ml amber ones with PTFE lined green caps ($2 ea or 3 for $5, or less for more than 10), then I also have some 120 ml ones, new in clear ($2 ea), new
amber with a plastic coating ($3 ea, ideal for bromine, TFA, and other hazardous acids), and used once but clean amber ones for $2 ea. I did a group
buy for a few people a few years ago and ended up with some left. For larger amounts I have a few 100 and 1000 ml media bottles left with white PTFE
lined caps, as well as a few other random bottles.Sulaiman - 10-12-2018 at 04:17
"Polycone" caps are polypropylene, that's the compatibility tables you need to look at.
The Polycone liner in a polycone/phenolic cap is polyethylene, not polypropylene. I'm not certain whether it is low- or high-density though.
Regardless I would not use a polycone liner for TMSCL. I store my TMSCL in an boston-round borosilicate glass container with an open-top cap having a
teflon/silicone liner over an inert atmosphere. This allows it to be syringed out. I transferred it from the manufacturer's container in a glove-bag
made by the company "Glas-Col".
